The main objectives of the proposal are to identify, purify and characterize the spermatozoal antigens capable of inducing immunologic infertility in rabbits. The role of secretory immunoglobulins, especially 1gA, produced by the female reproductive tract against spermatozoa will be examined in relationship to inhibition of both fertilization and early embryo development. Sperm antigens, such as the proteolytic enzymes and immobilizing-inducing factor, will be purified by different chromatographic and protein fractionation procedures. Heteroimmunization and isoimmunization against the different antigens to induce antibodies and isoimmune female rabbits will permit evaluation of possible involvement of the antigens in the fertility processes. Characterization of the antigens will be attempted by chemical, physical and immunochemical procedures. Antibody effects on sperm and embryos will be evaluated in both in vivo and in vitro systems.